Process of treating metallic filaments for electric incandescent lamps.



' WILHELM MAJERT, or BERLIN, GERMANY.

'raocnssor TREATING METALLIC F'ILAMENTs FOR ELE-oTRIeINc'ANDEscENT LAMPS.

T 0 all 'whom it may concern: I

Be it known that I, WILHELM MAJERT, a

subject of the King-of Prussia, residing at 17 Belle-Allianceplatz, Berlin, Germany,

-have invented certain new and useful Improvements in Processes of Treating Metallic Filaments for .Electric Incandescent Lamps; and I do hereby declare the following to be a full, clear, and exact description of the invention. i v

I am aware that by heating metallic filaments to a high temperature by means of the electric current, it is possible to clean the filaments and give them a more compact structure. These operations are performed while the filaments are in cacao or in a neutral gas-atmosphere which does not affect the filaments. Such neutral gases which do not afiect the filaments, are nitrogen, carbonic 0Xl(l"OI reducinggases, such as hydrogen, ammonia, water gas.

. By the intense heating up to approximately the melting point "of the metal used,

' impurities such as foreign metals of" low melting .point and boiling point, as for instance lead, silver, arsenic, zinc, as well as sulfur and carbon, are volatilized or con verted into dust, while the single particles of the highly fused metal that form the filament are welded more closely together.

Since the working in cacao requires a gradually increasing temperature and consequently a long period for. preventing an excessive loss of filaments during the ope'ra tion, working in practice usually takes place with atmospheric pressure or with a slight pressure above or below the atmospheric pressure in a. neutral gas-atmosphere as above stated. The intense heating of the metallic filaments only lasts a few seconds. The filaments thus produced however are not absolutely clean and also not of very compact structure Lam s made bymeans of such filaments usually ,la'cken after long use, the filament is not. so elastic and the lamp cannot burn under 1 watt current consum tion per Hefner candle power without the ament being very soon destroyed.

Now I have found that 'itis possible to produce a lamp with non-blackening filaments of very compact structure, which has only O,70,8 watt current consumption per Hefner candle power with a life of more than 900 burning hours, by subjecting the filaments to intense heat first, under ordinary Specification of Letters Patent. Application filed July 10, 1908. Serial No. 442,904.

Patented June 22, 1909.

terial in which order of succession t. e.

Whether first with atmospheric. pressure and then in vacuo, 0r first m rec 11.0 and then with: atmospheric pressure, the heating of the filaments to a high temperature by means of the electric current iseffected. If

the intense heating were to take place first" in 'vacuo and then in an atmosphere of neutralizing gas-under atmosphere ressure, the majority of the filaments would lie destroyed not only during quality of the ultimately produced filaments would also be inferior.

In practice, I carry out the process in the following manner: I- employ an apparatus which is used for preparing (equalizing) the carbon filaments by means of hydrocarbons. When the raw filaments are fastened between the pole-terminals and the glass globe is secured air-tight on the base, the globe is evacuated as completely as possible and then filled with a neutral gas, as for instance nitrogen, hydrogen, carbonic oXid, water gas (the known compound of hydrogen and carbonicoxid) o'rwith ammonlacal gas. Such apower-- the first operation but the ful electric current is then sent successively through each filament for 1 the filament'is heated approximately to its melting point. 'During each sudden flashing of a filament, it can be seen how it shortens to the extent of 25-50% according to its previous compactness and impurity andthat the impurities escape therefrom in the form of afine dark vapor. When all filaments are thus treated, the globe will be practically evacuated and the sin gle filaments now heated m racuo by the electric current 1n the is employed, it is advisable to send the current twice through the filaments alternately.

in different directions.

I cl aim The process of cleaning metallic filaments? for electric incandescent lamps and giving 2 seconds that 1 them a more com act structure, which con- I name to this specification, in the presence of sistsjn very higfly heating the filaments I two subscribing Witnesses. twice in succession by the electric current, the first time when they are in a neutral as- VVILHELM MAJERT 5 atmosphere and the second tilnewhen t ey X/Vitnessesz are in a practically evacuated space. JOHANNEs HEIN.

In testimony whereof I have signed my HENRY HASPER 

